secondssinceepoch

Seconds since epoch, often referred to as Unix time or epoch time, is a simple numeric representation of time as the number of seconds elapsed since a defined starting point called the epoch. On most Unix-like systems, the epoch is 00:00:00 UTC on 1 January 1970. A value of 0 corresponds to that moment, 1 is one second later, and so on. Some environments store sub-second precision by using fractional seconds or separate fields.

Representation and precision vary by platform and language. In many systems the core value is an integer time_t, which counts whole seconds. Some environments use 64-bit integers, extending the range far beyond 2038, while older 32-bit time_t can encounter the year 2038 problem. Other languages return seconds as a floating-point number to include fractions of a second, or provide milliseconds or nanoseconds as separate units. Converting to human-readable dates typically requires applying UTC or local time zone rules.

Usage is widespread in computing. Seconds since epoch serves as a timestamp for file metadata, logs, databases, network protocols, scheduling, and event timing. It provides a simple, monotonic measure suitable for arithmetic such as calculating durations or ordering events.

Limitations and caveats include leap seconds, which are not represented in the basic seconds-since-epoch count, possibly causing minor discrepancies with real-world timekeeping. Time values assume UTC; converting to local time requires time zone information and appropriate libraries. For high-resolution or robust timekeeping, developers may use additional fields or libraries that provide monotonic clocks or nanosecond precision.